U.S. patent number 5,355,253 [Application Number 07/974,108] was granted by the patent office on 1994-10-11 for stereoscopic retinal camera.
This patent grant is currently assigned to Nidek Co., Ltd.. Invention is credited to Tsuguo Nanjo, Tokio Ueno.
United States Patent |
5,355,253 |
Nanjo , et al. |
October 11, 1994 |
Stereoscopic retinal camera
Abstract
A stereoscopic retinal camera which enables the stereoscopic
observation of the fundus of the eye and is capable of
photographing the stereoscopic picture of the fundus by dividing a
light beam reflected by the fundus into two light beams and
transmitting the two light beams respectively along the light paths
of separate image forming optical systems. And according to the
stereoscopic retinal camera, each portion of the fundus and the
front portion of the eye is photographed by a focus adjustment
device, and an inter-image pitch between a right image and a left
image of photographing the fundus and/or the front portion of the
eye is corrected by an optical correcting device, whereby the
inter-image pitch caused by a difference of refracting power or by
a change of stereoscopic visual angle is obtainable not to be
changed.
Inventors: |
Nanjo; Tsuguo (Toyohashi,
JP), Ueno; Tokio (Chiryu, JP) |
Assignee: |
Nidek Co., Ltd.
(JP)
|
Family
ID: |
18351768 |
Appl.
No.: |
07/974,108 |
Filed: |
November 10, 1992 |
Foreign Application Priority Data
|
|
|
|
|
Nov 30, 1991 [JP] |
|
|
3-342184 |
|
Current U.S.
Class: |
359/473; 351/206;
351/216; 359/376; 396/18; 396/326 |
Current CPC
Class: |
A61B
3/132 (20130101); A61B 3/14 (20130101) |
Current International
Class: |
A61B
3/13 (20060101); A61B 3/14 (20060101); G02R
027/22 () |
Field of
Search: |
;351/206,216,211
;359/473,476,472,363,376 ;354/62 |
References Cited
[Referenced By]
U.S. Patent Documents
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|
|
4235540 |
November 1980 |
Hanamura et al. |
4634241 |
January 1987 |
Kohayakawa et al. |
|
Foreign Patent Documents
Primary Examiner: Ben; Loha
Assistant Examiner: Robbins; Thomas
Attorney, Agent or Firm: Parkhurst, Wendel & Rossi
Claims
What is claimed is:
1. A stereoscopic retinal camera which enables at least one of the
stereoscopic observation of the fundus of the eye and the
production of a stereoscopic picture of the fundus and a front
portion of the eye by dividing a light beam reflected by the fundus
into two light beams and transmitting the two light beams
respectively along the light paths of separate image forming
optical systems, said stereoscopic retinal camera comprising:
a focus adjustment means for photographing the fundus and the front
portion of the eye; and
an optical correction means for correcting an inter-image pitch
between a right image and a left image so as to be correspondent
when at least one of the fundus and the front portion of the eye is
photographed by operating said focus adjustment means;
wherein said focus adjustment means comprises an auxiliary optical
system for changing a focus area from the front portion of the eye
to the fundus or from the fundus to the front portion of the eye;
and
wherein said auxiliary optical system has a refracting power
corresponding to a difference between the refracting power of an
average eye and the refracting power of the front portion of the
average eye.
2. A stereoscopic retinal camera according to claim 1 wherein said
optical correction means is a deflective optical system for
changing a direction of the light beams.
3. A stereoscopic retinal camera according to claim 2, wherein said
deflective optical system has a prism function to compensate a
difference of inter-image pitch between a right image and a left
image when photographing the fundus of an average eye and the front
portion thereof.
4. A stereoscopic retinal camera according to claim 3, wherein said
deflective optical system is a deflection-angle prism.
5. A stereoscopic retinal camera which enables at least one of the
stereoscopic observation of the fundus of the eye and the
production of a stereoscopic picture of the fundus by dividing a
light beam reflected by the fundus along an optical path into two
light beams and transmitting the two light beams respectively along
light paths of separate image forming optical systems, said
stereoscopic retinal camera comprising:
a focus adjustment means disposed in the image forming optical
system in a conjugate relation with the fundus and the
photographing position; and
an optical correction means for correcting a difference of a
stereoscopic visual angle accompanying the operation of said focus
adjustment means;
wherein said optical correction means comprises a moving means for
moving a two-hole diaphragm for determining a stereoscopic visual
angle toward the optical path.
6. A stereoscopic retinal camera according to claim 5, wherein said
optical correction means comprises a mechanism which moves by
synchronizing with said focus adjustment means.
7. A stereoscopic retinal camera which enables at least one of the
stereoscopic observation of the fundus of the eye and the
production of a stereoscopic picture of the fundus by dividing a
light beam reflected by the fundus along an optical path into two
light beams and transmitting the two light beams respectively along
light paths of separate image forming optical systems, said
stereoscopic retinal camera comprising:
a focus adjustment means disposed in the image forming optical
system in a conjugate relation with the fundus and the
photographing position; and
an optical correction means for correcting a difference of a
stereoscopic visual angle accompanying the operation of said focus
adjustment means;
wherein said optical correction means comprises a variation means
for changing a distance between two-holes of a couple of two-hole
diaphragms for determining a stereoscopic visual angle.
8. A stereoscopic retinal camera according to claim 7, wherein said
optical correction means comprises a mechanism which moves by
synchronizing with said focus adjustment means.
9. A stereoscopic retinal camera comprising:
an objective lens for directing a light beam reflected from an
examinee's eye along an optical path, wherein the objective lens
focuses the reflected light beam to a first point A when the
examinee's eye is at a first position located a first distance D
from the objective lens, and further focuses the reflected light
beam to a second point A' when the examinee's eye is at a second
position located a second distance D' from the objective lens;
optical means for splitting the reflected light beam into a right
light beam and a left light beam and for respectively directing the
right light beam and the left light beam to a right optical path
and a left optical path;
focusing means, located in the right and left optical paths, for
focusing the right light beam and the left light beam to form a
first set of stereoscopic images at a first image point B and a
second image point Ba on a film plane when the objective lens
focuses the reflected light beam to the first point A, wherein the
first set of stereoscopic images have an inter-image pitch P, and
for focusing the right light beam and the left light beam to form a
second set of stereoscopic images at a third image point B' and a
fourth image point Ba' on the film plane when the objective lens
focuses the reflected light beam to the second point A', wherein
the second set of stereoscopic images have an inter-image pitch P'
that is different from the inter-image pitch P of the first set of
stereoscopic images; and
optical correction means that can be selectively placed in the
right and left optical paths, wherein the optical correction means
causes the inter-image pitch P' of the second set of stereoscopic
images to be corrected to the inter-image pitch P of the first set
of stereoscopic images, wherein the second set of stereoscopic
images are formed at the first and second image points B, Ba.
10. A stereoscopic camera as claimed in claim 9, wherein the first
set of stereoscopic images are images of the fundus of the
examinee's eye and the second set of stereoscopic images are images
of a front portion of the examinee's eye.
11. A stereoscopic camera as claimed in claim 9, wherein the
optical correction means is a deflective optical system.
12. A stereoscopic camera as claimed in claim 11, wherein the
deflective optical system includes a deflection-angle prism.
13. A stereoscopic camera as claimed in claim 9, further comprising
an illuminating optical system for illuminating the examinee's eye
with an illumination light beam.
14. A stereoscopic camera as claimed in claim 9, further comprising
an observation optical system for selectively receiving the first
and second sets of stereoscopic images.
15. A stereoscopic camera as claimed in claim 9, wherein the
focusing means includes an auxiliary focusing means that can be
selectively placed in the right and left optical paths when the
objective lens focuses the reflected light beam to the second point
A'.
16. A stereoscopic camera as claimed in claim 15, wherein the
auxiliary focusing means comprises auxiliary lenses.
17. A stereoscopic camera as claimed in claim 9, wherein the
optical correction means has a predetermined optical correction
factor that corresponds to the correction factor necessary to
correct the inter-image pitch P' of the second set of stereoscopic
images to the inter-image pitch P of the first set of stereoscopic
images for an average eye.
18. A stereoscopic retinal camera which enables at least one of the
stereoscopic observation of the fundus of the eye and the
production of a stereoscopic picture of the fundus of the eye by
dividing a light beam reflected by the fundus into two light beams
and transmitting the two light beams respectively along the light
paths of separate image forming optical systems, said stereoscopic
retinal camera comprising:
a focus adjustment means for photographing the fundus and the front
portion of the eye; and
an optical correction means for correcting an inter-image pitch
between a right image and a left image so as to be correspondent
when at least one of the fundus and the front portion of the eye is
photographed by operating said focus adjustment means;
wherein said focus adjustment means comprises an auxiliary optical
system for changing a focus area from the front portion of the eye
to the fundus or from the fundus to the front portion of the eye.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stereoscopic retinal camera, and
more particularly relates to a mechanism to amend a fluctuation of
a stereoscopic visual angle or an inter-image pitch or the like
which is caused by a difference of a portion to be photographed or
a refracting power of an examinee's eye.
2. Description of Related Art
A conventional optical system of a stereoscopic retinal camera is
as shown in FIG. 7. The construction of the optical system is
similar to the system of the embodiment of the present invention
which will be mentioned later. In the apparatus of FIG. 7, the
light beam reflected by the fundus of an examinee's eye 14 is
focused at point A in an inverted image by an objective lens 13,
and passing through an aperture of a perforated mirror 12, the
light beam is split into two light beams by a two-hole diaphragm
15. The separated light beam is interchanged to a right light beam
and a left light beam, the image distance is extended. If there is
a defective sight ametropy in the examinee's eye, the photographer
moves a focusing lens 19 to a direction of the optical path, so
that the fundus image of the eye i s formed on a film 21. In the
case of normal eye, the position of the first intermediate image at
point A is moved to A.sup.- side direction along with the optical
axis on nearsight, and moved to opposite A.sup.+ side direction on
farsight. Therefore, the inter-image pitch on a field stop 27 and a
film 21 is changed, whereby a stereoscopic visual angle is changed.
This changing is extremely inconvenient for prosecuting a
stereoscopic measurement precisely.
Further, there is provided an apparatus which is able to photograph
not only eye's fundus, but also a front portion of the eye, in
general retinal cameras. Such a kind of apparatus comprises a
convex auxiliary lens which is disposed in the photographing
optical system insertably. If this kind of mechanism for
photographing the front of the eye is adopted on the stereoscopic
retinal camera, the stereoscopic visual angle is changed largely,
and the inter-image pitch is also changed to small size P' within a
range of size P, shown in FIG. 2.
Accordingly, the synthesized area as a stereoscopic image becomes
narrow, and a problem is caused in the direct vision of the
stereoscopic image.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above
circumstances and has an object to overcome the above problems and
to provide a stereoscopic retinal camera which can photograph and
observe the fundus and/or the front portion of the eye by a
certified stereoscopic visual angle, inspire of a defective sight
ametropy of the examinee's eye.
The second object of this present invention is to provide a
stereoscopic retinal camera which is obtainable a full area of
stereoscopic image when the front portion of the eye is
photographed from near side.
Additional objects and advantages of the invention will be set
forth in part in the description which follows and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and attained by means of the instrumentalities and
combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the
invention, as embodied and broadly described herein, the
stereoscopic retinal camera of this invention comprises a focus
adjustment means for photographing each portion of the fundus and
the front portion of the eye, and an optical correct means for
correcting an inter-image pitch between a right image and a left
image so as to be correspondent when the fundus and/or the front
portion of the eye is photographed by operating the focus
adjustment means.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute
a part of this specification illustrate an embodiment of the
invention and, together with the description, serve to explain the
objects, advantages and principles of the invention. In the
drawings,
FIG. 1 is a diagrammatic side view of the optical systems of a
stereoscopic retinal camera in a first embodiment according to the
present invention;
FIG. 2 is a diagrammatic top view of the optical systems of the
stereoscopic retinal camera of FIG. 1, which shows a photographing
condition that an auxiliary lens 30 is disposed in an optical path
of a photographing optical system and a wedge-shaped
deflection--angle prism 31 is disposed out of the photographing
optical path;
FIG. 3 is a diagrammatic top view of the optical systems of the
stereoscopic retinal camera of FIG. 1, which shows a photographing
condition that both of the auxiliary lens 30 and the
deflection-angle prism 31 are disposed in the photographing optical
path;
FIG. 4 is a diagrammatic top view of the optical systems of a
stereoscopic retinal camera in a second embodiment according to the
present invention, which explains a mechanism that a right and left
apertures of two-hole diaphragms 15 (15a and 15b) are moved in
synchronizing to focusing lenses 19 (19a and 19b);
FIG. 5 is a partial diagrammatic view in perspective of the camera
of FIG. 4;
FIG. 6 is also a diagrammatic top view of the optical systems of
the stereoscopic retinal camera shown in FIG. 4, which explains a
mechanism that the two-hole diaphragms 15 (15a and 15b) are moved
according to the movement of an intermediate image A toward a
direction of the optical axis ; and
FIG. 7 is a diagrammatic side view of the optical systems of a
stereoscopic art retinal camera as one prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A detailed description of one preferred embodiment of a
stereoscopic retinal camera embodying the present invention will
now be given referring to the accompanying drawings.
In FIG. 1, there is shown a stereoscopic retinal camera in a first
embodiment according to the present invention, which comprises an
illuminating optical system, a photographing optical system and an
observation optical system.
Illuminating Optical System
The illuminating optical system comprises a halogen lamp 1, i.e., a
light source of illumination for observation, condenser lenses 2, a
xenon flash lamp 3, i.e., a light source of illumination for
photographing, a beam splitter 4, a relay lens 5, an aperture
diaphragm 6, a mirror 7 for deflecting an light path, an
illuminating relay lens 8, an index plate 9 provided with a central
black point 10 for eliminating detrimental light, an illuminating
lens 11, a perforated mirror 12 and an objective lens 13. The
halogen lamp 1 and the xenon flash lamp 3 are in a conjugate
relation with respect to the condenser lenses 2. The aperture
diaphragm 6 is provided with a circular slit. An intermediate image
of the slit is formed near the opening of the perforated mirror 12,
the intermediate image of the slit is reflected by the perforated
mirror 12 and the objective lens 13 focuses the image of the slit
near the cornea to illuminate the fundus of the eye 14.
Photographing Optical System
A two-hole diaphragm 15 is in a conjugate relation with the pupil
of the eye 14 with respect to the objective lens 13. The two-hole
diaphragm 15 splits the light beam into two light beams as shown in
FIG. 2. Indicated at 16 and 17 (17a and 17b) are light beam
splitting prisms. The light beam splitting prism 16 interchanges a
right light beam and a left light beam with each other, and the
light beam splitting prisms 17 (17a and 17b) collimate the two
light beams so that the collimated light beams pass along two
parallel paths separated from each other by a predetermined
distance.
The light beam reflected by the fundus of the eye 14 is focused at
a point A in an inverted image by the objective lens 13, passes
through the opening of the perforated mirror 12, the two-hole
diaphragm 15, the light beam splitting prisms 16 and 17 (17a and
17b), relay lenses 18 (18a and 18b), focusing lenses 19 (19a and
19b) and image forming lenses 20 (20a and 20b). The image forming
lenses 20 (20a and 20b) form the image of the fundus on the film
21. The focusing lenses 19a and 19b are movable along the optical
axis of the photographing optical system. The positions of the
focusing lenses 19a and 19b are adjusted according to the
refracting power of the eye 14 to focus the image of the fundus on
the film 21.
A swing mirror 22 can be turned between a position to reflect the
light beam toward the observation optical system and a position to
allow the light beam to pass along the optical axis of the
photographing optical system to the film 21. In photographing the
picture of the fundus, the swing mirror 22 is turned up in the
direction of the arrow in synchronism with the flashing action of
the xenon flash lamp 3 to allow the light beam reflected by the
fundus to fall on the film 21.
Auxiliary lenses 30 (30a and 30b) are disposed in the photographing
optical path insertably to change the focusing area from the fundus
to the front portion of the eye. In the embodiment of the
apparatus, the focus adjusting area formed by the focusing lenses
19a and 19b are provided for photographing the fundus as a center
on OD (Zero Diopter), and the area is not enough for photographing
the front portion of the eye, which requires strong diopter +D.
Accordingly, it is covered by inserting an auxiliary lens which
have powers determined based on the position of the above mentioned
standard point A'.
A thin wedge-shaped deflection-angle prism 31 (31a and 31b) is
disposed in the photographing optical path with the auxiliary
lenses 30 (30a and 30b) to correct the angle of the optical axis.
As shown in FIG. 2, in case of photographing the front portion of
the eye, the working distance is extended to D' from D which is the
working distance for photographing the fundus. Therefore the
intermediate image is moved to A' from A by the objective lens 13,
the inter-image pitch P' becomes narrow against the inter-image
pitch P for photographing the fundus. The deflection-angle prisms
31a and 31b are inserted into the optical path, the inter-image
pitch P is extended (shown in FIG. 3). The degree of the
deflection-angle prism 31 (31a and 31b) are selected so that the
pitch P between two scenes on the film 21 in case of photographing
the fundus (defective sight ametropy OD, working distance D) and
the pitch P' in case of photographing the front portion of the eye
by inserting the deflection-angle prisms 31(31a and 31b) correspond
with each other. P' is an inter-image pitch whence the focusing is
corresponded to the front portion of the average examinee's eye
under the highly useful working distance D'
Observation Optical System
The observation optical system and the photographing optical system
use the objective lens 13, the swing mirror 22 and the components
between the objective lens 13 and the swing mirror 22 in common.
When observing the fundus, the swing mirror 22 is set on the light
path of the photographing optical system to reflect the observation
light beam reflected by the fundus and passed through the
components from the objective lens 13 through the focusing lenses
19a and 19b toward mirrors 23a and 23b. The observation light beam
reflected by the mirrors 23a and 23b passes through observation
image forming lenses 24a and 24b, focusing glasses 27a and 27b, and
oculars 25a and 25b, and fall on the right eye 26a and the left eye
26b of the observer.
The operation of the stereoscopic retinal camera thus constructed
will be described hereinafter.
The stereoscopic retinal camera is mounted on a movable table, not
shown, which is moved relative to a fixed table by a sliding
mechanism. The examinee's head is held on a head support fixed to
the fixed table, and the halogen lamp 1 is turned on to illuminate
the eye 14. In case of photographing the fundus of the eye, the
observer operates the sliding mechanism to align the image of the
aperture diaphragm 6 on the cornea with the pupil of the eye 14 so
that the fundus is illuminated properly in proper working distance
D. In case of photographing the front portion of the eye, the
operator extends the working distance to D' from D. The
illumination light is expanded wholly and the front portion of the
eye is illuminated properly.
In case of photographing the fundus of the eye, the light beam
reflected by the fundus is focused to form an inverted image of the
fundus at the point A. The light beam passed the perforated mirror
12 is split into a right light beam and a left light beam by the
two-hole diaphragm 15. The light beam splitting prism 16 disposed
directly behind the two-hole diaphragm 15 interchanges the right
light beam and the left light beam. Then, the light beams are
deflected by the prisms 17a and 17b, and the deflected light beams
are focused in erect images of the fundus at each point B and Ba on
the film 21 by the pair of image forming lens systems including the
relay lenses 18a and 18b, the focusing lenses 19a and 19b, and the
image forming lenses 20a and 20b. The observer views the erect
images for the stereoscopic observation of the fundus.
The observer turns the focusing knob during the binocular
observation of the images to focus the focusing lenses 19a and 19b
and makes the fine adjustment of the alignment of the image of the
aperture diaphragm 6 with the pupil of the eye 14 so that flares of
the illuminating light will not appear around the right and left
images.
After the operations for aligning the image of the aperture
diaphragm 6 with the pupil of the eye 14 and for focusing the
focusing lenses 19a and 19b have been completed, a shutter release
button is depressed. Then, the swing mirror 22 is lifted up and the
xenon flash lamp 3 flashes synchronously to form the image of the
fundus on the film 22.
As shown in FIG. 2, in case of photographing the front portion of
the eye, the operator extend the working distance to D' from D
which is the working distance when the fundus is photographed, the
photographing area of the front portion of the eye is maintained
properly. At that time the intermediate image is moved to plus side
position A' from position A by the objective lens 13. Then the
auxiliary lenses 30a and 30b are inserted into the optical path to
compensate for lack of focus adjusting area of the image forming
optical system by the focusing lenses 19a and 19b. By inserting the
auxiliary lenses 30a and 30b, the front portion images B' and Ba'
of the eye are formed on the film 21, as the inter-image pitch P'
becomes narrower than the inter-image pitch P which is the pitch
when the fundus is photographed, the operator may insert the
deflection-angle prisms 31a and 31b into the optical path, whereby
the inter-image pitch is extended to P (shown in FIG. 3). The
operation being continued is almost same as the operation of
photographing the eye's fundus, therefore the detail explanation of
the operation is omitted.
The automatic operations of the stereoscopic retinal camera are
controlled by the microcomputer mounted in the apparatus.
The present invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. For instance, if the image forming optical system having
the focus adjusting area sufficiently, the auxiliary lenses 30a and
30b are not necessary to be provided, and a concave lens is
inserted into the optical path when the eye's fundus is
photographed. Further, the deflection-angle prism is employed in
this embodiment to accomplish the angle-correction of the optical
axis with simple constitution, variety of constitutions well known
for angle-correction, are able to be adopted.
In FIG. 4, there is shown the arrangement of the optical system in
a second embodiment, and FIG. 5 shows a partial view in perspective
of the optical system. The character of the second embodiment
consists in the constitution of the two-hole diaphragm. The
explanation of other part of the constitution is omitted, as it is
already explained in the first embodiment.
The two-hole diaphragms 15 (15a and 15b) are disposed in a
conjugate relation with the pupil of the examinee's eye with
respect to the objective lens 13. Further, the right and left
apertures of the respective two-hole diaphragms 15a and 15b is
constituted as to be moved in synchronizing with the focusing
lenses 19a and 19b. FIG. 5 shows the mechanism being synchronized
mechanically, as one example. That is to say, the two-hole
diaphragm 15 consists of a couple of aperture plates 15a and 15b,
having pins 33, 33 thereon respectively. The aperture plates 15a
and 15b are pulled toward each other by a spring 36 which is
connected to the pins 33, 33. When the focusing lenses 19a, 19b are
moved toward front and rear direction by operating a diopter
adjusting knob 34, the pins 33, 33 are moved to be away or come
near along a guide groove (not shown in FIG. 5) which is formed on
a side of a guide plate 35, the aperture plates 15a, 15b are moved
to an arrow direction shown in FIG. 5, whereby the distance between
center points of both apertures of the aperture plates 15a, 15b is
changed. The quantity of movement is determined according to the
moving distance of the first intermediate image formed by
refracting power of the examinee's eye. The shape of the guide
groove is formed in relation to the moving quantity of the focusing
lenses 19a, 19b, so that the ratio of distance between the two-hole
diaphragms 15a, 15b and the distance from the two-hole diaphragms
15a, 15b to the intermediate image is fixed.
In that case, it is not necessary to connect the movement of the
focusing lenses 19a, 19b and the center distance of the apertures
of the aperture plates 15a, 15b, it is proper to provide the moving
mechanism of the aperture plates 15a, 15b by detecting the moving
quantity of the focusing lenses 19a, 19b by using a shaft encoder
or the like.
The mechanism of controlling two movements such as mentioned above
is known variously, therefore the explanation of the mechanism is
omitted, but the present invention is not intended to be
limited.
In case of the above second embodiment, the two-hole diaphragms
15a, 15b are moved to separate each other synchronizing to the
movement of the focusing lenses 19a, 19b, the same effect is
obtained by the mechanism that the two-hole diaphragms 15a, 15b
move to the same direction and same distance of the movement of the
first intermediate image A along the optical axis. This embodiment
is shown in FIG. 6.
In this FIG. 6, the above mentioned two-hole diaphragms 15a, 15b
are moved to the front and rear direction (i.e. optical direction)
along the optical path by synchronizing with the movement of the
focusing lenses 19a, 19b for focusing the lens according to the
refracting power of the examinee's eye. That is to say, the
two-hole diaphragms 15a, 15b are moved to the objective lens 13
when the refracting power is on near sightedness side and are moved
to the light beam splitting prism 16, 17a, 17b side respectively,
and the quantity of the movement of the two-hole diaphragms are
determined to be equal to the quantity of the movement of the first
intermediate image which is moved according to the refracting power
of the examinee's eye, whereby the stereoscopic angle faced to the
first intermediate image against the optical axis a and b, is
always hold constant. And because the stereoscopic angle is held
constant, the change of the pitch between two images on the film 21
is also able to stay small.
Further, according to each of the above mentioned embodiments, the
change of the stereoscopic visual angle is amended against the
defective sight ametropy perfectly, but it is able to add the
modification, for example, to amend the angle by degrees in a
certain permission range, without departing from the spirit and the
scope of the invention. And also it is purposeful to combine the
mechanism of the above mentioned second embodiment with the
mechanism of the above mentioned first embodiment.
The foregoing description of the preferred embodiment of the
invention has been presented for purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form disclosed, and modifications and
variations are possible in light of the above teachings or may be
acquired from practice of the invention. The embodiment chosen and
described in order to explain the principles of the invention and
its practical application to enable one skilled in the art to
utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated. It
is intended that the scope of the invention be defined by the
claims appended hereto, and their equivalents.
* * * * *